Psychological predictors of adherence to lifestyle changes after bariatric surgery: A systematic review

Abstract Objective Adherence to lifestyle changes after bariatric surgery is associated with better health outcomes; however, research suggests that patients struggle to follow post‐operative recommendations. This systematic review aimed to examine psychological factors associated with adherence after bariatric surgery. Methods PubMed, PsycInfo, and Embase were searched (from earliest searchable to August 2022) to identify studies that reported on clinically modifiable psychological factors related to adherence after bariatric surgery. Retrieved abstracts (n = 891) were screened and coded by two raters. Results A total of 32 studies met the inclusion criteria and were included in the narrative synthesis. Appointment attendance and dietary recommendations were the most frequently studied post‐operative instructions. Higher self‐efficacy was consistently predictive of better post‐operative adherence to diet and physical activity, while pre‐operative depressive symptoms were commonly associated with poorer adherence to appointments, diet, and physical activity. Findings were less inconsistent for anxiety and other psychiatric conditions. Conclusions This systematic review identified that psychological factors such as mood disorders and patients' beliefs/attitudes are associated with adherence to lifestyle changes after bariatric surgery. These factors can be addressed with psychological interventions; therefore, they are important to consider in patient care after bariatric surgery. Future research should further examine psychological predictors of adherence with the aim of informing interventions to support recommended lifestyle changes.

recommended lifestyle changes.Therefore, it is important to improve the current understanding of the factors that predict post-operative adherence in the bariatric surgery setting.
Numerous reviews have examined psychological predictors of weight loss outcomes following bariatric surgery, which include (but are not limited to) depressive disorders, substance misuse, and disordered eating 3,[6][7][8] but there has been less of focus on predictors of adherence to post-operative instructions regarding lifestyle changes.There are two existing systematic reviews of factors associated with post-operative adherence that focused on a range of demographic (e.g., age and unemployment) and clinical (e.g., preoperative BMI) predictors. 5,9While knowledge of these factors is valuable in identifying individuals at greater risk of poor postoperative adherence, they are not modifiable and, thus, can be of limited clinical utility.The review by Hood and colleagues included psychological factors 5 ; however, this review contained studies published up until September 2015 and is therefore missing more updated findings.
In order to improve knowledge around factors that can be addressed in clinical practice, the present systematic review aimed to specifically examine clinically modifiable psychosocial predictors of adherence to common treatment instructions after bariatric surgery.
For the purposes of this review, the term "psychological" is defined as factors pertaining to psychological wellbeing (e.g., mental health symptoms and disorders, emotional experiences) and cognition (e.g., self-efficacy, beliefs about adherence).This definition was kept broad in order to capture a wide range of factors that may be of clinical relevance.

| Search strategy
PubMed, PsycInfo, and Embase were searched to identify relevant articles from the earliest searchable paper through to August 2022 using keywords and MeSH terms related to two broad concepts: (1)   bariatric surgery and (2) patient adherence or compliance.The search terms were based on the search strategies used in existing systematic reviews in the areas of bariatric surgery and treatment adherence, alongside discussions with a research librarian (see Supplementary File for the full search strategy).The search was kept broad in order to capture all studies that measured the relationship between a psychological factor and adherence.Additionally, the reference lists of included articles were hand-searched to identify relevant papers that were missed in the initial searches.

| Study selection
A total of 1023 abstracts were located through the database searches and hand-searching (see Figure 1 for the flowchart of study selection).After removing duplicate results, 891 papers were independently screened by two raters (JC and a research assistant).Inclusion criteria were (1) included patient adherence to instructions after bariatric surgery as an outcome; (2) examined clinically modifiable psychological factors associated with post-operative adherence; (3) had an adult population (i.e., aged 18 years or older); and (4)   written in English.Exclusion criteria were (1) did not have original data (e.g., reviews or editorial pieces); (2) examined only demographic, clinical, or surgical factors associated with adherence; (3)   was a case study, trial, or qualitative study, which did not present data on the association between psychological variables and an adherence outcome; and (4) was not peer-reviewed.Studies were included only if they were considered relevant by both raters and any discrepancies were resolved by a third rater (LV).A total of 32 studies met inclusion criteria and were coded independently by two raters using a coding sheet developed for the purposes of this review.

| Data extraction
The following data were coded from the included papers: country where the study was conducted, demographic variables, surgical procedure, time since surgery, and study design.The raters also coded the post-operative recommendations(s) that were assessed with relation to adherence (e.g., diet, physical activity, follow-up appointment attendance, support group attendance, and vitamin/ supplement use).The selection of these recommendations was guided by the American Society for Metabolic and Bariatric Surgery (ASMBS) Guidelines 10 and discussions with bariatric clinicians.
The psychological factors that were investigated as predictors of adherence in each study were coded as "positively associated", "negatively associated", or "not associated".Although most papers also presented data on demographic and clinical factors associated with adherence, only data related to psychological predictors or correlates of adherence were extracted as these were the outcome measures for this review.In the case of missing data, attempts were made to contact the study's corresponding author via email for further information; however, not all authors responded.Where no response was received, missing data was indicated with "N/A".

Study quality was assessed using the Joanna Briggs Institute (JBI)
Critical Appraisal Checklist for Analytical Cross-Sectional Studies. 11e measure comprises eight items designed to measure the potential risk of bias in study design, conduct, and data analysis.The items cover possible biases in participant recruitment, study sample, validity and reliability of measures used to define exposure, condition, and outcomes, identification/control of confounding factors, and appropriate choice of statistical analysis.The satisfaction of each criterion was rated as "yes", "no", "unclear", or "not applicable" by two independent raters (JC and LV).A study quality rating was given based on the number of criteria rated "yes".Studies with low ratings

| Study quality
The study quality ratings ranged from 3 to 8 (M = 6.34), with a maximum score of 8.All studies satisfied the criteria for adequate definition of inclusion criteria.The criterion that was least frequently satisfied was related to strategies to manage confounding factors, with only 50% of studies adequately controlling for confounds in their analyses.Table 1 shows the number of studies that satisfied each of the items in the JBI Critical Appraisal Checklist, and the study quality ratings are included in Table 2.
The certainty in this body of evidence may be impacted by the presence of mixed findings for some treatment instructions (although, significant effects are generally in the same direction), the small number of studies available for some post-operative instructions, the variability in measures of adherence, and variability in study quality.

| Psychological predictors of adherence
For appointment attendance, dietary adherence, and physical activity, the studies included in this systematic review were organized into subsections on (1) mental health symptoms and/or disorders and (2)   beliefs/cognitions that were associated with adherence to postoperative instructions.These subsections were not used for the remaining outcomes (support group attendance, adherence to supplement use, and adherence to multiple instructions) because there were relatively few studies included.

| Mental health factors
Studies investigating psychological factors related to adherence to medical and/or allied health follow-up appointments have focused primarily on emotional or mental health variables (see Table 2 for summary).In two studies of gastric bypass and sleeve gastrectomy patients, having a history of any psychiatric condition was linked to poorer appointment attendance in the first 24-36 months after surgery. 12,13Similarly, laparoscopic adjustable gastric band (LAGB) patients who had not attended any appointments in the previous 12 months were more likely than adherent patients to report that post-operative mental health problems acted as a barrier to attendance. 14However, other studies have failed to find the same association: specifically, pre-operative experience of "negative emotions", 12 pre-operative psychiatric diagnoses, 15,16 and psychiatric "stability" (i.e., having either no psychiatric history or well-managed symptoms) 17 were not predictive of follow-up appointment attendance.
Specific mental health disorders have also been investigated in relation to appointment adherence.Pre-operative diagnosis of depression, high levels of depressive symptomology, and a history of pharmacological treatment of depression were predictive of missing follow-up appointments in the 24 months after gastric bypass surgery in three separate studies. 13,18,191][22][23] In studies examining anxiety, higher levels of pre-operative phobic anxiety 20 and an avoidant attachment style were associated with a lower likelihood of appointment attendance in the first 6-12 months post-surgery. 21However, there was no significant link between adherence and generalized anxiety 15,20 or an anxious attachment style 21 in other studies.
Other behavioral and emotional disorders have also been examined in the context of post-operative adherence.Pre-operative behavioral problems (e.g., antisocial behaviors and substance use) were associated with poorer follow-up appointment attendance 1 year after surgery. 24In contrast, pre-operative emotional/internalizing dysfunction, 24 hostility, interpersonal sensitivity, alexithymia, 20 and maladaptive eating attitudes and habits 23 were not significantly related to follow-up appointment adherence.
T A B L E 1 Numbers and percentages of studies meeting the quality rating criteria of the JBI critical appraisal checklist for analytical cross-sectional studies.

Studies satisfying criterion, n (%)
Were the criteria for inclusion in the sample clearly defined?

(100%)
Were the study subjects and the setting described in detail?

(97%)
Was the exposure measured in a valid and reliable way?

(78%)
Were objective, standard criteria used for measurement of the condition?

(50%)
Were the outcomes measured in a valid and reliable way?

(69%)
Was appropriate statistical analysis used? 31 (97%) Patients' beliefs about adherence, about bariatric surgery itself, and about their surgeon have also been studied in relation to appointment attendance.Patients who reported low levels of motivation to attend follow-up appointments and/or to lose weight after surgery, 14 and those who felt uncomfortable attending appointments, 25 were more likely to have missed all follow-up appointments in the preceding 12 months than were patients who did not endorse those views.Conversely, patients were more likely to attend post-operative appointments if they reported a "good" or "very good" relationship with their bariatric surgeon compared with those reporting a "poor" or "very poor" relationship. 26However, adherence was not significantly correlated with readiness to change before surgery, 27 nor with beliefs that adherence is too difficult, expectations concerning the outcomes of bariatric surgery, or perceived social/family support. 14ving limited health literacy and health numeracy has also been associated with a higher likelihood of missed and "no show" postoperative appointments, respectively.spective study, those who had higher scores on self-report measures of positive affect and self-esteem also demonstrated greater improvements in their adherence to dietary recommendations from week 20 to week 92 post-surgery. 29Likewise, a prospective cohort study of 230 patients found that pre-operative self-esteem and body satisfaction were positively correlated with dietary adherence 1 year after Roux-en-Y Gastric Bypass (RYGB) surgery. 30 contrast, pre-operative depressive symptoms were negatively associated with dietary adherence in two prospective studies. 29,31tients who reported higher levels of depressive symptoms were more likely to identify as being "almost adherent" rather than "generally adherent" at 6 and 12 months after surgery, where the latter category was reflective of better adherence. 31Similarly, preoperative negative affect predicted less improvement in patients' dietary adherence over time. 29Another study also demonstrated a negative correlation between pre-operative depressive symptoms and dietary adherence, but depressive symptoms were not a significant individual predictor of adherence in a regression model that also included pre-operative night-eating, readiness to limit food, and years of dieting experience. 30pressive symptoms assessed after surgery also significantly predicted patients' classification as adherent (i.e., adhered approximately/more than half of the time) or non-adherent (i.e., adhered less than half of the time) to dietary recommendations. 32Other studies have found that having a history of mental health help-seeking, 31 a history of sexual and/or physical abuse, 13 and higher levels of preand post-operative generalized anxiety symptoms 31,32 were also negatively predictive of dietary adherence in the 6-24 months after RYGB surgery.Although attachment anxiety was similarly associated with poorer dietary adherence, attachment avoidance did not demonstrate a link to adherence. 31Contrary to the findings above, a separate study did not find a significant association between preoperative generalized anxiety and dietary adherence. 30e literature has also identified eating disorders, disordered eating behaviors, and eating-related attitudes that are associated with dietary adherence.A history of purging, 13 pre-operative emotional eating, 33 pre-operative grazing (i.e., picking/nibbling), 33 pre-operative night-eating, 30 or a history of combined mood and eating disorder 34 is predictive of poorer adherence to dietary recommendations in RYGB and gastric band patients.Poorer dietary adherence has also been associated with higher frequency of selfreported grazing, mindless eating, eating foods outside their dietary plan, after-dinner eating, "capitulating" (i.e., over-eating following perceived failure in dietary adherence), and loss of control after bariatric surgery. 35However, this was reported in a paper with a relatively low study quality rating (4/8).Conversely, patients who, prior to surgery, reported feeling more prepared to limit their food intake demonstrated better adherence after surgery, and those who reported having higher levels of eating-related cognitive restraint showed greater improvements in adherence over time. 29,30

| Cognitive factors
Beyond these mental health factors, studies have also explored whether patients' cognitions about adherence are related to their dietary adherence behaviors.In a study of 153 female RYGB patients, both post-operative maintenance self-efficacy (i.e., confidence in one's ability to adhere to treatment instructions) and post-operative relapse self-efficacy (i.e., confidence in one's ability to get back on track after a lapse in adherence) were significant positive predictors of adherence. 32In the same study, patients who utilized action planning (i.e., planning details needed to adhere to recommendations) as a coping strategy reported higher levels of dietary adherence compared with those who used this strategy less frequently.However, no significant relationship was identified between coping planning (i.e., planning what to do in the face of barriers to adherence) and dietary adherence.Another study found that, postoperatively, a stronger intention to adhere, a more positive attitude toward adherence, and higher self-efficacy regarding adherence were associated with better dietary adherence. 36nally, the role of internalized stigma has also been investigated with relation to dietary adherence.In a study of 298 patients who received RYGB or vertical sleeve gastrectomy within the 5 years prior to participation, those who had higher levels of internalized weight stigma were found to be at increased risk of engaging in disordered eating such as frequent snacking and perceived loss of     control over food consumption. 37The internalized stigma was also negatively correlated with patients' self-assessed adherence to postoperative dietary recommendations.This finding was replicated in a separate study of 112 patients, in which weight bias internalization was associated with poorer self-reported dietary adherence (but not with adherence to fluid intake recommendations), even when controlling for age, gender, time since surgery, BMI, and surgery type. 38wever, perceived weight stigma within healthcare settings specifically (e.g., weight-related discrimination from health professionals) was not associated with dietary adherence. 37Conversely, dietary adherence was positively associated with a stronger endorsement of social support or positive social norms related to dietary adherence. 366 | Physical activity

| Mental health factors
Five studies evaluated the predictive value of mental health factors (including eating disorders) on patients' exercise adherence. 13,30,34,39,40Self-reported depressive symptoms before surgery were negatively predictive of physical activity in RYGB patients 12 months after surgery. 30Similarly, pre-operative psychosocial stress has been associated with poorer exercise adherence.A study of 119 LAGB and RYGB patients reported that those who were classified as experiencing "great psychosocial stress" (defined as meeting criteria for at least one of: depression, binge-eating disorder, or psychosocial problems in a self-report measure) were less likely to engage in regular exercise. 39However, this relationship was significant only in female participants.
In a study of RYGB patients, having a history of both mood and eating disorders was associated with a lower likelihood of exercising at least 5 days per week when compared with patients who reported no previous diagnoses, and compared to those who reported only a mood disorder or an eating disorder. 34That study did not report whether a statistically significant difference in adherence existed between those with just one psychological disorder and those with no disorders.Cross-sectionally, higher scores on measures of optimism and positive affect were associated with a higher frequency of engaging in moderate-to-vigorous physical activity (but not with time spent walking) after bariatric surgery. 40However, this relationship was no longer significant once depression and anxiety were controlled for.Bergh and colleagues (2016) also assessed preoperative night eating and binge eating in a cohort of RYGB patients and failed to find a significant relationship with physical activity levels 12 months after surgery.Surprisingly, in a separate study, having a history of sexual and/or physical abuse was correlated with better exercise adherence in the first 24 months after RYGB surgery. 13No significant relationships were found between exercise adherence and measures of pre-operative anxiety, emotion regulation, resilience, body satisfaction, self-esteem, or relationship satisfaction. 30beliefs about the benefits of the behavior), subjective norms, and perceived behavioral control. 41The overall model of the TPB was significantly predictive of both intention to exercise and actual leisure-time physical activity (i.e., physical activity that is not related to work, transportation, or household chores) 6-9 months after surgery, and more than 12 months after surgery. 42Out of the three components of the TPB, post-operative perceived behavioral control (which is similar to self-efficacy) was the strongest and most consistent predictor of exercise adherence.A separate study also found a significant correlation between pre-operative self-efficacy and exercise adherence. 30Likewise, pre-operative planning for physical activity (e.g., what exercises to do, when to do them, and how to overcome barriers to exercise) was positively associated with exercise adherence.Conversely, weight bias internalization was negatively associated with time spent engaging in moderate-to-vigorous activity (but not time spent walking). 38Finally, views that patients reported before surgery, such as readiness to increase physical activity and expectations about wellbeing and social outcomes after surgery, were not significant predictors of exercise adherence. 30

| Support group attendance
Predictors of adherence to support groups or behavioral health groups (more akin to group therapy) were examined in three studies. 20,43,44One study examined the relationship between behavioral health group attendance and pre-operative depression, alexithymia, and psychiatric symptoms (i.e., hostility, anxiety, and interpersonal sensitivity) in a group of RYBG patients. 20The behavioral health group utilized a cognitive-behavioral approach to address issues related to post-operative psychosocial adjustment, social support, adherence, and mindful eating.That study found that patients who attended fewer than two out of four behavioral groups in the first 12 months after surgery were more likely to have higher levels of pre-operative hostility, generalized anxiety, and phobic anxiety compared to those who attended three to four groups. 20wever, these differences were only significant in univariate analyses.When hostility, anxiety, and phobic anxiety were included as predictors alongside travel distance (i.e., between the bariatric clinic and patients' homes) in a multivariate logistical regression, the psychosocial variables were no longer significantly predictive of group attendance.Travel distance remained a significant predictor in the regression, which suggests that it may explain behavioral group attendance over and above psychosocial factors.
Another study of RYGB patients found that self-reported mood (both pre-and post-operative) as well as emotional or psychosocial problems (operationalized as psychiatric treatment-seeking and use of psychotropic medications after surgery) were not significantly associated with support group attendance. 43In the third study, 44 researchers investigated the views of patients who underwent bariatric surgery regarding in-person support group meetings.These views included patients' beliefs about the usefulness, necessity (for weight loss), and helpfulness of support group attendance.No significant differences in views were found between those who had never attended a post-operative support group and those who had attended at least one group, although non-attenders were marginally (p = 0.07) more likely than attenders to think that support groups would have no effect on weight loss and to think that support groups are not needed post-surgery.Note, however, that the latter two studies had relatively low ratings (3/8) on the measure of study quality.

| Adherence to supplement use
Only one study presented data on adherence to vitamin supplements after bariatric surgery. 38In this cross-sectional survey study of 112 patients after sleeve gastrectomy and gastric bypass, greater weight bias internalization was associated with poorer adherence to recommended supplements.

| Adherence to multiple instructions
Three studies measured adherence to a combination of postoperative instructions.In a small study of LAGB patients (N = 18), "non-compliers" (seven patients who were non-adherent to dietary recommendations and two patients who failed to attend any followup appointments for at least 12 months) were compared to nine control patients (randomly selected patients who had the same surgeon as the "non-compliers"). 33No differences between the groups were noted with regard to pre-operative binge eating disorder, bulimia nervosa, mood disorders, alcohol abuse, child sexual abuse history, insight about obesity, and the belief that the band is responsible for weight loss, but non-compliers were more likely to report pre-operative emotional eating.Another study examined the relationship between personality traits and affect and found that "overall adherence" (comprising diet, physical activity, fluid intake, and supplement use) was positively associated with post-operative positive affect and dispositional optimism. 40The third study examined adherence to vitamin use alongside other post-operative recommendations (e.g., dietary instructions, refusing to be weighed) under the category of 'weight-loss instructions', 13 but no data were presented regarding psychological predictors of adherence to weight-loss instructions.

| DISCUSSION
Pre-operative depression/depressive symptoms were commonly associated with poorer adherence to post-operative instructions, including dietary recommendations, 29,31 follow-up appointment attendance, 13,19 and exercise. 30Although six studies did not report a significant relationship between adherence and mood disorders/ depressive symptoms, no studies identified a positive correlation between low mood and adherence.There was no discernible pattern of differences between the studies that identified a negative relationship compared to those that did not find a significant relationship in terms of study design, measures used to assess mood, and treatment instruction.Thus, pre-operative depressive symptoms appear to be a relatively consistent predictor of poorer adherence after bariatric surgery.
Likewise, pre-operative disordered eating behaviors and attitudes were consistently associated with poorer post-operative dietary adherence.This highlights the need to thoroughly assess for and treat maladaptive eating habits before surgery, particularly as patients may believe, prior to surgery, that their surgery would extinguish unhelpful eating behaviors. 45Therefore, patients should be offered education to manage expectations and support to address disordered eating behaviors before and after surgery.[48] The results for anxiety in its various forms were less clear.
Generalized anxiety, 31,32 phobic anxiety, 20 and attachment anxiety 31 were identified as barriers to adherence in some studies, but other studies did not find a significant association between generalized anxiety and post-operative adherence. 15,20,30This variability did not appear to be related to the method used to assess anxiety.Research on the anxiety/adherence relationship in other chronic conditions has similarly found weak associations. 49It may be that some forms of anxiety are associated with better or poorer post-operative adherence while other forms are unrelated, and identifying these relationships would be a worthwhile aim for future research.
When mental health factors were evaluated, it was common for studies to assess pre-operative symptoms or diagnoses as opposed to post-operative levels of these variables.Knowledge that preoperative depression, for example, predicts post-operative adherence is undoubtedly useful as it allows the identification of individuals at increased risk of poor adherence.Where appropriate, clinicians could recommend psychological or pharmacological treatments for depression as part of patients' preparation for bariatric surgery to mitigate the risk of suboptimal outcomes.It is equally informative, however, to know whether post-operative depression similarly impairs adherence.Only one study measured post-operative depression (using the Patient Health Questionnaire 50 ), finding that it was associated with a greater likelihood of being mostly nonadherent to post-operative dietary instructions. 32This may suggest that there is a need for clinicians to monitor and manage depression post-operatively to increase adherence and optimize treatment outcomes.
Another important factor to evaluate post-operatively may be cognitions (i.e., thoughts/beliefs) related to adherence, which was examined in only a few studies.Perceived behavioral control and selfefficacy after surgery were identified as facilitators of post-operative CHAN and VARTANIAN

3. 5 |recommendations 3 . 5 . 1 |
Dietary Mental health factorsMental health disorders or symptoms were among the most commonly evaluated psychological factors with regard to dietary adherence.Pre-operative positive affect, self-esteem, and body satisfaction were positively linked to dietary adherence.In a pro-

A B L E 2
Study characteristics and psychological factors associated with adherence after bariatric surgery.

3. 6 . 2 |
Cognitive factors In addition to psychological disorders or mental health factors, patients' beliefs have been linked to exercise adherence as well.This research has focused on beliefs that fall within the framework of the Theory of Planned Behavior (TPB), which encompasses attitudes (i.e.,

Country Bariatric procedure Sample size Sex (%F); Age (M, SD); Pre-operative BMI (M, SD) Follow-up time/ time since surgery Study quality rating (0-8) Study design Measure of adherence Measure of psychological predictor Psychological predictors (Positive [Pos], Negative [Neg], Non- significant [NS])
-CHAN and VARTANIAN T A B L E 2 (Continued) Study (Year); T A B L E 2 (Continued) Study (Year);

Country Bariatric procedure Sample size Sex (%F); Age (M, SD); Pre-operative BMI (M, SD) Follow-up time/ time since surgery Study quality rating (0-8) Study design Measure of adherence Measure of psychological predictor Psychological predictors (Positive [Pos], Negative [Neg], Non- significant [NS])
-CHAN and VARTANIAN T A B L E 2 (Continued) Study (Year);